Building Better Tomatoes April 29, 2002
Fresh from the Vine?
One little gene may be all that stands between a fresh, juicy, homegrown tomato and its bland, store-bought counterpart. Earlier this month, biologists announced that they've identified the gene that controls the ripening process in the humble fruit. If this "rin" gene can be manipulated effectively, scientists will be able to create breeds of tomatoes that will be more flavorful even after the long journey from the vine to the produce department.

Today, tomatoes are plucked from the vine early, when still green and firm, to ensure that they survive shipping without bruising and rotting. Picking tomatoes early means they have less chance to develop flavor, color, and nutrients naturally. By manipulating the rin gene, scientists will be able to slow the ripening process, letting the tomato develop on the vine for longer — but still keeping it firm enough to ship safely.

The scientists responsible for the rin gene findings are from the U.S. Department of Agriculture and the Boyce Thompson Institute for Plant Research, on the campus of Cornell University. They hope that their technique may also be applied to other fruits — such as strawberries, bananas, bell peppers, and melons — which suffer from the same shipping and storage complications.

The developments seem promising but, as genetically modified (GM) foods, these designer fruits may not be welcomed by all. GM foods have been nicknamed "Frankenstein foods" ("Frankenfoods" for short) by critics who fear that scientists are creating a monster they know little about. Is it wise to alter Earth's species by tampering with DNA? Is it wise to splice DNA from one species into another's genetic code — e.g., from a fish to a strawberry? Will there be unforeseen, frightening consequences for Earth's ecosystems, or will the result be abundant, high-quality food to feed the world's hungry? These are the questions heard over and over in the GM food debate.

Proponents say that GM crops can be cultivated for superior flavor, nutritional value, and pest-resistance, with higher yields and lower production costs. They also say that humans have been performing a sort of crude genetic engineering, in the form of selective breeding, since the beginning of civilization; splicing DNA can be seen as modern technology's precise, refined version of the same process.

Critics say that the science of genetic engineering is not refined enough. Mothers for Natural Law, an environmental group, says that because the double helix is so delicate and so full of mysteries, human efforts at manipulating it are "like performing heart surgery with a shovel." Chief among the cited dangers are the introduction of unknown allergens into foods; mutations that could cause toxicity; the spread of "pollutant" DNA that could upset the balance among species in the biosphere; and engineered pest-resistant plants that could cause super-pests to evolve, wreaking havoc. The Sierra Club says that "genetic engineering poses a very grave threat to the natural environment."

On the whole, the people of Europe are inclined to agree. Since June 1998, the European Union has enforced a moratorium on licensing new GM products until rigorous testing, labeling, and tracing regulations are put in place (these are still being reviewed by some of the Union's 27 member nations). Very little land is devoted to the production of GM crops because farmers are unwilling to fly in the face of public opinion.

The European distaste for GM foods is the cause of much tension between the EU and the United States. Top US trade negotiator Robert Zoellick has threatened to protest to the World Trade Organization, accusing Europe of being protectionist and unfairly blocking US exports.

There is much at stake for the GM-food-friendly United States, which is one of the world's four major producers of GM crops (the others are Argentina, Canada, and China). According to The Sierra Club, over 60% of all processed foods purchased by US consumers are manufactured with GM ingredients. The percentage of acres of GM soybeans and corn have increased sharply since 1995 (see a graph from the United States Department of Agriculture) and levels are projected to increase in 2002.

Some pundits say that the GM food debate is about to open up into a transatlantic food fight. Your students can learn about this hot issue by first studying the techniques scientists use to genetically engineer plants, and then having an ethical discussion about the potential advantages and disadvantages of GM foods.

The Flavr Savr
A genetically engineered tomato known as the "Flavr Savr" was launched in 1994. Its genetic code was modified to enable it to stay on the vine for longer and delay rotting. The public was very wary of the much-hyped tomato; this together with production problems meant that the Flavr Savr flopped with consumers.

Starlink Corn
Corn crops were at the center of one of the most notorious episodes in the history of GM foods. In September 2000, an unapproved, gene-altered corn variety was found in taco shells being sold in grocery stores across the United States. The shells contained corn that had been approved as animal feed only. The corn, called "Starlink," had been genetically modified in a way that made it difficult to break down in the human digestive system, and therefore was more likely to cause reactions in the people who ate it. Products containing Starlink were recalled.

Learn About the Problem
The following activities are taken from High School Biology Gateways. To use them, you need to be a Riverdeep subscriber, or you can get a free 30-day trial. You'll also need the Logal Express plug-in.

  • Students who are new to the topic of DNA should begin with the Biology Gateways activity: DNA and Replication.
  • Then they can learn how scientists modify seeds genetically in the Biology Gateways activity: Genetic Engineering.

Think About the Problem
In the Genetic Engineering activity, students ligate DNA fragments from one organism to another of the same species. GM foods often ligate DNA fragments from one species to another. Ask students:

  • Will the genetically engineered segment of DNA be passed on to the organism's offspring?
  • Could unforeseen mutations occur from generation to generation?

Students can share their views on GM foods by answering the following questions:

  • If you knew that the salad in front of you contained genetically modified tomatoes, would you eat it? Explain your answer.
  • Do you think that consumers should have a choice between eating GM and non-GM foods? Should GM foods be labeled? Why or why not?

Divide the class in two, and have each group prepare a debate for and against continued use of GM foods. Insist that the students base their arguments on science, not on subjective claims. Students can equip themselves for the debate by visiting the Web sites listed in the "Extending the Problem" section below.

Have students consider various human innovations in the world food supply, e.g., pasteurization, hybridization, pesticides, irradiation. Ask them:

  • What were the initial expectations and fears surrounding these innovations?
  • Did the innovations turn out to be positive or negative for human health and for the environment in general?

Extending the Problem
The World Wide Web is brimming with resources on GM foods. Here is a selection for you and your students:

Overview of GM foods: Many Web sites present both sides of the debate and explain the science of genetic engineering.

  • Students can explore the complex arguments on both sides of the GM food debate with Harvest of Fear, a Frontline and Nova Special that includes interactive activities in which students can compare the traditional method of selective breeding with the latest transgenic methods.
  • The American Association for Advancement of Science has a SCOPE forum on GM foods. The forum was launched in February of this year to give the public space for informed debate. It includes a section for educators.
  • New Scientist's Hot Topics: GM Foods
  • A clear and intelligent overview of the debate is available at BBC.com in the article "The power of genes."
  • Resources are plentiful at Yahoo's Full Coverage page on the Genetically Modified Food Debate. Of special interest is the constantly-updated list of news stories.

In favor of GM foods: According to Bill Gates, "Genetically modified food has met fierce opposition among well-fed Europeans, but it's the poor and the hungry who need it most."

Against GM foods: Students can visit the Web sites of prominent anti-GM-foods organizations.

Engineering human DNA: The Riverdeep Current has some useful resources for you and your students.

  • You can guide your students in an investigation of cloning — of both animals and humans — with "Cloning Controversy," a Teaching the News article.
  • Have students read "Changing the Blueprint," which explains the various applications of human cloning (including using stem cells to cure disease) and asks students to consider various ethical questions.

Students can also take the following Riverdeep Internet field trips:

    Questions? Comments? Write to the editor: editor@riverdeep.net